1. Field of the Invention
The present invention relates to a device for radiating an ultrasound into a material by means of using a piezoelectric substrate, an interdigital arrangement of two comb-shaped electrodes formed on an upper end surface of the piezoelectric substrate, a counter electrode formed on a lower end surface of the piezoelectric substrate, an interdigital transducer, and an amplifier.
2. Description of the Prior Art
For the purpose of radiating an ultrasound into a liquid, a thickness mode piezoelectric transducer with parallel plate-like electrodes is usually used. Such a conventional type of transducer has a difficulty in controlling the radiation angle into the liquid, and particularly in radiation toward a slant direction. In addition, the conventional type of transducer has a difficulty in high-frequency operation. On the other hand, an interdigital transducer on the piezoelectric substrate operates at a liquid-solid boundary as a leaky wave transducer for bulk wave radiation into the liquid. The leaky SAW traveling on a sufficiently thick substrate compared with the wavelength has only one mode without velocity dispersion. Thus, conventional transducers such as the thickness mode piezoelectric transducer and the interdigital tansducer for the leaky SAW have the problem of the limited ultrasound-radiation angle.